Acta Photonica Sinica, Volume. 51, Issue 10, 1012001(2022)
Development and Applications of Laser Induced Fluorescence Photobleaching Anemometer（Invited）
Figures & Tables(19)
Fig. 4. Schematic diagram of MRV velocity measurement for gas flow profiling in open-cell foams［90］
Fig. 7. Schematic diagram of a typical LIFPA system based on different microscopes
Fig. 8. Normalized fluorescent intensity distribution
Fig. 10. Velocity profiles in cylindrical and rectangular microchannels［104］
Fig. 12. Measuring the rise time of electroosmotic flow and its distribution in a microcapillary［105］
Fig. 13. Diagram of the electrokinetic micromixer and the experimental results on velocity field［100］
Fig. 15. Diagram of ACEOF microchannel and the experimental results by LIFPA［95］
Fig. 16. Time series of dimensionless velocity fluctuations in oscillating electroosmotic flow［109］
Fig. 17. Velocity power spectra at different AC frequency and the influence of the control parameters on the state of the electroosmotic flow［113］
Table 1. Common flow velocity measurement techniques in microfluidics
View tableView in ArticleTable 1. Common flow velocity measurement techniques in microfluidics
Velocity
measurement
techniques
Principles Specifications Applications and
requirements
µPIV Taking particle images in the field of interest. Calculating the displacements of particles between two adjacent frames. Then，by dividing the time interval of the two adjacent images，the velocity field can be obtained √ 2D/3D velocity field
√ Non-invasive
√ Euler representation
√ Relatively high temporal（~30 μs）and spatial（order of μm）resolutions
× Suffers the influence of particle lagging and electric field
Need to add particle tracers in the working fluid，appropriate for gas or liquid with good transparency，e.g. water，blood，oil and etc PTV Taking particle images in the field of interest. Calculating the displacements of particles between two adjacent frames. Then，by dividing the time interval of the two adjacent images，the velocity field can be obtained √ 2D/3D velocity field
√ Non-invasive
√ Lagrange representation
√ Velocity field near complex boundary
√ Translational and rotational velocity fields
√ Relatively high temporal（~30 μs）and spatial（~submicrons）resolutions
√ Suffers the influence of particle lagging and electric field
Need to add particle tracers in the working fluid，appropriate for gas or liquid with good transparency，e.g. water，blood，oil and etc MTV Mark the flow field which is mixed with long-lifetime fluorescent molecules by laser-induced fluorescence with modulated light patterns，e.g. parallel lines，grids，spot array/matrix. Monitoring the movement/deformation of the patterns by taking images. Calculating the displacement of flow through the movement/deformation of the patterns between two adjacent images. Then，the velocity field can be calculated based on the displacement and the time interval of two adjacent images √ 2D velocity field
√ Non-invasive
√ Tracing the flow by long-lifetime fluorescent molecules. Visualize the flow field simultaneously.
√ Avoid the influence of particle lagging and electric field
× Complex algorithms
× Relatively low temporal resolution（~ms），but high spatial resolution（~submicrons）in microfluidics
× Inappropriate for continuous measurement in complex and temporally fluctuated flow fields
Need to add long-lifetime fluorescent dye in the working fluid，appropriate for gas or liquid with good transparency OCT Capturing the images of particles in the flow field by OCT. Calculating the displacements of particles between two adjacent frames. Then，by dividing the time interval of the two adjacent images，the velocity field can be obtained √ 2D velocity field
√ Non-invasive
√ Appropriate for low-transparency fluids
× Relatively high spatial resolution（order of μm），but poor temporal resolution
× Proper particle concentration in the fluids
Low-transparency fluids with particles/cells/tissues and etc，e.g. biofluids MRV Capturing the images of particles/samples in the flow field by Magnetic Resonance Imaging. Calculating the displacements of particles/samples between two adjacent frames. Then，by dividing the time interval of the two adjacent images，the velocity field can be obtained √ 2D velocity field
√ Non-invasive
√ Appropriate for non-transparent fluids
× Low temporal and spatial（order of mm）resolutions
× A strong magnetic field is applied during imaging of the flow field，where metallic materials should be avoided
Non-transparent fluids with particles/cells/tissues/bubbles and etc，e.g. biofluids LIFPA Calculating flow velocity by measuring the fluorescence after photobleaching，relying on the velocity-fluorescence relationship × 1D velocity magnitude
× Single point
× Need calibration
√ Non-invasive
√ High temporal resolution（order of μs）
√ High/Super spatial resolution（~200 nm/70 nm）
√ Avoid the influence of particle lagging and electric field
Need to add fluorescent dye with relatively poor photostability in the working fluid，appropriate for uniform liquid with good transparency and low autofluorescence
Table 2.
Table 2.
Diameter/μm Experimental/ms Theoretical/ms Deviation/% 50 0.69 0.43 60 75 1.39 1.01 37
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Wei ZHAO, Yu CHEN, Zhongyan HU, Chen ZHANG, Guiren WANG, Kaige WANG, Jintao BAI. Development and Applications of Laser Induced Fluorescence Photobleaching Anemometer（Invited）[J]. Acta Photonica Sinica, 2022, 51(10): 1012001
Paper Information
Category: Instrumentation, Measurement and Metrology
Received: Nov. 9, 2021
Accepted: Apr. 15, 2022
Published Online: Nov. 30, 2022
The Author Email: WANG Kaige (wangkg@nwu.edu.cn)
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